<script>
  const s = new Set([
    ['foo', 1],
    ['bar', 2],
  ])
  const m1 = new Map(s)
  console.log(m1.get('foo'), m1.get('foo1'))

  const m2 = new Map()
  let key = ['a']
  m2.set(key, 1111)
  console.log(m2.get(key))

  const m3 = new Map([
    ['a', 1],
    [new Date(), 2],
    [null, 3],
  ])
  console.log([...m3.keys()])
  console.log([...m3.values()])
  console.log([...m3.entries()])

  const arr2 = []
  {
    const a = [] // 计数：1
    {
      const b = a // 计数：2
    } // 计数： 1
    arr2[0] = a // 2
  } // 计数：1
  // 垃圾搜集
</script>
